Due to the wisdom of the federal government my main source of lead is disappearing. I was getting it from wheel weights, but with the new composition that is changing. So besides buying it where do you get your lead?
As far as cheap to free? never did that. I bought mine in ingots a few years ago and don't even remember what I paid.
Lead sources that I know of:
Wheel weights (not anymore apparently)
There are weights in some pellet guns and airsoft guns for realistic handling (it's probably cheaper to get it elswhere)
Some electronics in small amounts (maybe one bullet per 10 cellphones)
Recycling centers may be able to help you out. No idea on quality though.